Voice is an invisible instrument, at the same time more complex than any other, but much can be learned from analogy with other musical instrument. The production of sound, the resonance and pitch controlling mechanisms of voice can be compared to those of string or wind instruments, thus drawing useful conclusions.
The beautiful art of singing, one of the greatest achievements of humankind, is conceived in the mind of a singer who interprets the musical, artistic and intellectual intentions of the composers. But to actually produce it, while meeting the aesthetic demands of the audience, the singer uses parts of his own anatomy – muscles, bones and cartilages. The metaphorical language, traditionally employed by singing teachers over the last few centuries can, surprisingly, be much clarified by resorting to how the anatomy of the singing apparatus actually works. The centuries-old and ambiguous terms such as chest and head voices or falsetto can be explained in terms of muscle actions
Voice acoustics deals with the production of powerful, resonant and uniform voice. The subject revolves around two main factors: a voice source or vibrator, which produces a set of harmonics, and a vocal tract filter or resonator, which selectively strengthens or weakens frequencies that are introduced into it by the voice source. Each resonator has its own preferred frequencies, called formants. The effect of the interactions between these two factors, mainly by “tuning” the formants is the primary concern of acoustic voice pedagogy.
Vocal registers are one of the most talked about - and yet still misunderstood - concepts in voice training. This is because the term “register” means different things to different people. Registers occur because the vocal folds are capable of producing several different vibratory patterns. Modern science defines four registers in human voice, of which practically just one – the modal register - is used in classical singing. The historical definitions of “chest” and “head” registers are outdated as trained singers always blend the two making them just one register with varying contribution of the chest and head mechanisms.
Every singer, be aware or unaware of it, has a vocal strategy that he/she developed in order to produce volume, equalise the timbre across the vocal range, or just “sound well”. The strategy is developed by training in trained singers, and to some extent by intuition or sometimes chance in untrained ones. Getting the right mix of chest/head voices in each note of the scale, bridging the resonance gap between the “turn” and the whoop timbres (especially in females) by modifying articulators or choosing the vowel in formant tuning, covering, and making harmonics and formats to co-operate, are the main challenges in developing the vocal strategies.
We recognise a resonant voice when we hear it but is not so easy to define; it is rich in harmonic content, vibrant, with some nasality, a ring or a twang. It carries over the orchestra because it has higher harmonics enhanced by higher formants (sinter’s formant). However, at a higher level it turns out that a more likely source of resonance is the reinforcement of vocal fold vibration by an “inertive” vocal tract, which feeds energy back to the source of sound, thereby strengthening its harmonic content.